In general, mobile communication systems have been developed to provide communication services while guaranteeing user mobility. Thanks to rapid technological advancement, mobile communication systems are capable of providing not only voice communication services but also high-speed data communication services.
In recent years, the 3rd Generation Partnership Project (3GPP) has been working to standardize specifications for the Long Term Evolution (LTE) system as a next generation mobile communication system. The LTE system aims to realize high-speed packet based communication supporting a data rate of about 100 Mbps exceeding existing data rates. To achieve this, various approaches have been considered, such as reducing the number of nodes on a communication path through simplification of the network architecture and bringing wireless protocols as close as possible to wireless channels.
Meanwhile, in a data service, unlike a voice service, allocable resources are determined according to the amount of data to be sent and channel conditions. As such, in a wireless communication system such as a mobile communication system, the scheduler manages or allocates transmission resources in consideration of the amount of transmission resources, channel conditions, and the amount of data. This applies also to the LTE system viewed as a next generation mobile communication system, where the scheduler placed at the base station manages and allocates radio transmission resources.
When data to be sent to the base station is generated, the user equipment sends a scheduling request for necessary resources to the base station. Here, transmission of the scheduling request may succeed or fail.
Currently, when transmission of a scheduling request fails, the user equipment tends not to record the procedure of sending the scheduling request and the base station is unaware of this failure, making it difficult to efficiently manage radio resources.